1. Field of the Invention
The present invention relates to a process for producing a sulfur modified polychloroprene.
2. Detailed Description of the Prior Art
Heretofore, a solvent soluble sulfur modified polychloroprene has been produced by polymerizing chloroprene in an aqueous emulsion by using a peroxide catalyst in the presence of sulfur and then peptizing the resulting polymer by adding a sulfur-containing organic peptizing agent such as tetraalkylthiuramdisulfide and dialkyldithiocarbamate and the like. However, in this process, since sulfur-containing organic peptizing agents such as tetraalkylthiuramdisulfide have been used, it has been difficult to completely terminate the peptization at a desired level. Accordingly, the Mooney viscosity of the latex and also the solid rubber content of the product disadvantageously varies in the storage of the product. It is known that the storage stability of the latex can be improved by including an alkali bisulfide or persulfate in the peptization using the sulfur-containing organic peptizing agent. It is also known that a sulfur modified polychloroprene having storage stability can be produced by polymerizing chloroprene or a mixture of chloroprene and a small amount of a comonomer in an aqueous emulsion in the presence of 0.01-2 wt. % of sulfur and 0.01-1.5 wt. % of dialkylxanthogendisulfide. However, the product of this process is not fully satisfactory. Consequently, there is a need for an improved process for preparing a sulfur modified polychloroprene.